Aromatic carbonate polymers are well known, commercially available materials having a variety of applications in the plastics art. Such carbonate polymers may be prepared by reacting a dihydric phenol, such as 2,2-bis(4-hydroxyphenyl)propane, with a carbonate precursor, such as phosgene, in the presence of an acid binding agent. Generally speaking, aromatic polycarbonate resins offer a high resistance to the attack of mineral acids, may be easily molded, and are physiologically harmless as well as stain resistant. In addition, such polymers have a high tensile and impact strength (except in thick molded sections), and a dimensional stability surpassing that of many other thermoplastic materials. However, in certain applications, the use of aromatic polycarbonate resins is limited because they exhibit severe environmental stress crazing and cracking. "Environmental stress crazing and cracking" refers to the type of failure which is hastened by the presence of organic solvents such as, for example, gasoline, particularly high octane no lead gasoline, acetone, heptane and carbon tetrachloride as well as basic type solvents such as alcohols, amines and the like when such solvents are in contact with stressed parts fabricated from aromatic polycarbonate resin. The most significant effect is a loss in vital impact strength and an increased brittle type failure in the standard Notched Izod test system. Contact with such solvent may occur depending upon the application to which the compositions are being applied. Certain formulations of polycarbonate have been devised which increases the resistance of polycarbonate to environmental stress cracking, for example polycarbonate and a minor amount of a polyalkylene terephthalate such as polyethylene terephthalate or polybutylene terephthalate. However these formulations generally have a significantly lowered thin section impact resistance compared to polycarbonate itself. Impact modifiers such as acrylates and polyolefins are often times added to such formations to bring about increased impact resistance.
It has been recently discovered that the addition of an acrylate elastomer and a phenoxy resin to a major amount of an aromatic polycarbonate retained impact strength and ductility when exposed under test conditions to a standard brake fluid comprising primarily ethers and alcohols. The same compositions did not perform well when exposed to a high aromatic gasoline under the same test conditions, see our earlier filed U.S. Ser. No. 747,784, filed June 24, 1985. It has now been found that such a combination of acrylate elastomer and phenoxy resin will provide similar impact resistance characteristics to an aromatic polycarbonate-polyalkylene terephthalate blend. Additionally, the presence of a further impact modifier, an olefin acrylate, does not significantly adversely affect the retention of impact resistance in an alcohol and amine system of the stressed fabricated part as long as the weight of acrylate elastomer exceeds the weight of olefin acrylate by more than about two to one.